Forget fiction and non-fiction. There are two types of writing: prescriptive and descriptive. If it reads like instructions, telling you what to do and what will work, it's prescriptive. But if it details what's possible, what you could do, what happened - it's descriptive.
I don't want to write prescriptively anymore.
The problem is that there are so many people telling other people on the internet what they should do. Too many frameworks and rules for making money, finding love and fulfilment. Too much certainty. Too much shouting. The internet is at its best when it inspires people to go out and make their own mistakes.
My totally unfounded belief is that the lessons from descriptive works, though less obvious and surface-level, sink in more deeply. You integrate and internalise them better because you worked for them. They have a higher chance of changing your life.
This is most true in fiction, where you have to really engage with the story to find what it wants to teach you. But you remember it, don't you?
Descriptive writing has a distinct advantage for the writer, too. It's easier. When you're writing something prescriptive, you feel like there must be a watertight thesis holding your words together to make them worth everyone's time. At least I do. Describing, on the the other hand, holds it's own weight. It's enough for you to simply tell your story, to note your observations.
If your writing doesn't turn out to be useful, then at the very least it's art.